Process of making projection welding type composite contacts



C. B. PROCESS OF MAKING PROJECTION WELDING May 24, 1966 GWYN, JR

TYPE COMPOSITE CONTACTS Original Filed Nov. 16, 1960 United StatesPatent PROCESS OF MAKING PROJECTION WELDING TYPE COMPOSITE CONTACTSChildress B. Gwyn, In, Export, Pa., assignor, by mesne This applicationis a division of my co-pending application, Serial Number 69,639, filedNovember 16, 1960,

and now United States Patent 3,191,273.

The present invention relates to processes for making projection weldingtype composite contacts, and more particularly to such contacts in whicha steel backing member is indented and has elements of contact elementmaterial placed therein.

A highly satisfactory type of electrical contact is one having a backingor support of relatively hard material, such as steel, with one face ofthis backing or support carrying a contact made of silver or the like.Such a contact is shown in my prior Patent No. 2,199,240.

Several methods are known by which the above described contact can bemade. In one known method, a button is provided by blanking and forminga contact from a sheet of clad or overlay material. That is to say, theinitial sheet may comprise steel with an overlay of silver. The contactproduced by this method is of satisfactory quality, but the method hasmany disadvantages, among which are a high scrap loss. In addition, inthis method, tolerances, materials temper and ratios of componentmaterials must be held to very exacting limits. These requirementsfurther increase the cost of the end product, so that all in all, thisprocess is a relatively expensive one.

In another known process, the backing metal members are first blanked orformed from steel strip, are then electroplated with nickel, copperor'the like, where desired, and then subsequently deposited intorefractory boats or jigs. The desired contact facing material, such assilver, is then blanked from a sheet and placed upon the surfaces of thesteel backing members, which are usually disks, and then the refractoryboat or jig, loaded as described, is heated in an oven in order to fusethe silver contact element to the steel backing member. This process,which is described in my Patent No. 2,049,771 has been found to requirea relatively large heating source, because of the refractory boat orjig. Since these boats or jigs generally are made of or contain carbonor graphite mixtures, the steel backing members absorb some of thecarbon, and this results in embrittlemen-t, blistering, peeling, etc. Inaddition, it has been found that the contact facing material does notuniformly flow over the surface of the backing member, in all cases, andthis results in final products which have only a thin facing of contactmaterial near the outer edges thereof.

An object of the present invention is to provide a process formanufacturing composite contacts of satisfactory quality with economy ofcost.

Yet another object of the present invention is the provision of aprocess for making composite contacts in which the use of refractoryboats or jigs is eliminated.

A further object of the present invention is to provide a process whichwill require the consumption of less heat thanheretofore in order tomanufacture composite contacts.

A still further object of the present invention is the provision of aprocess for making composite contacts which will avoid the absorption ofcarbon or graphite, and

thereby eliminate the production of contacts that are brittle, subjectto blistering, peeling, etc.

Another object of the present invention is to provide a process formaking composite contacts in which the contacts produced will have asuitably thick and uniform facing of contact material.

Other objects and many of the attendant advantages of the presentinvention will be readily understood from the following specificationand drawings, wherein:

FIGURE 1 is a plan view of a blank of weldable base material prepared inaccordance with the invention.

- FIGURE 2 is a cross-sectional view showing the deposition of a contactelement in the sheet of FIGURE 1.

FIGURE 3 is an enlarged cross-sectional view of the structure shown inFIGURE 2, after heating.

FIGURES 4 through 8 are cross-sectional views illustrating successivesteps in the removal of an individual contact from the backing materialstrip.

FIGURE 9 is a cross-sectional view of the product produced by thisprocess.

Referring now to the drawings, wherein like or corresponding referencenumerals are used to designate like or corresponding parts throughoutthe several views, there is shown in FIGURE 1 a sheet '20 of weldablebase material, such as steel. Sheet 20 may be of any length, and inpractice the length of sheet or strip 20 is limited only by productionand transportation factors. The sheet 20, which will be understood to bea blank, has therein a plurality of indentations 21, the indentations 21being produced by known embossing or coining operations and beingcircular in the embodiment shown. .There are a great number of theindentations 21 provided in the sheet 20, so that production may proceedat a rapid rate.

Referring now to FIGURE 2, there may be seen in cross-section a part ofthe sheet '20, the indentation 21 being shown as having placed therein abutton or contact element 22 which is, conventionally, of silver. What'-ever the materials of the sheet 20 and element 22, it will be understoodthat the element 22 will have a lower melting point than the sheet 20.It will be observed that the bottom wall 23 of indentation 21 has acentral depres- 25, and that the silver element 22 has crept up thewalls of the indentation 21 as is indicated at 26. There is also aconvex upper surface 27 of the melted and solidified element 22.

Subsequent to the removal of the sheet 20, or a portion thereof, fromthe furnace, the steel strip may be passed to a conventional punch presswhere the individual indentation 121 with the melted and solidifiedelement 22 will come under a punch 30 which is above a coining die 31 ina die body 32. Punch 30 and die body 32 will be caused to move towardseach other, viewing FIGURE 4, the action continuing as shown in FIGURE 5wherein it may be seen that the punch 30 has moved into contact with thesheet 20, entering into the identation 21, while the coining die 31 hasmoved into position to receive that material which will be punched fromthe sheet 20, and comprising the melted and solidified contact element22, together with the indentation bottom wall 23.

FIGURE 6 shows the Shearing action completed, with separation of theparts from sheet 20 and FIGURE 7 shows the further progression of punch30 which now compresses the sheared element 22 and bottom wall 23against the coining die 31 in die body 32. FIGURE 8 shows the upwardmovement of punch 30, and the downward movement of coining die 31,carrying with it the completed composite contact 35. Contact '35 isshown in FIGURE 9, after having been removed from the coining die 31 asby blowing or the like, and may be seen to comprise a backing member 36having a central button 37, to the upper surface of which is fused agenerally arcuate silver contact element 38, it being understood thatthe element 38 was formerly the element 072 and that the backing member36 formerly was the bottom wall 23 of indentation 21.

It will be understood, of course, that while the upper surface ofelement 38 is shown convex, and that this is due to the shape of thepunch, 30, this shape is given by way of illustration only and whereother shapes are desired the punch 30 may be provided with such othershapes.

In the process above disclosed, due to .the fact that the indentationsmay be made and loaded in such large quantities and with such greatrapidity as is provided by fast operating punching machines, theproduction of composite contacts may proceed at an extremely rapid rate.This will substantially reduce the cost of the end product. Further,since it is unnecessary to provide jigs or boats which will consume heatand contaminate the contact elements, there is a further advantage inthe economy of production and quality of the end product.

It will be obvious to those skilled in the art that various changes maybe -made without departing from the spirit of the invention and,therefore, the invention is not limited to What is shown in the drawingsand described in the specification, but only as indicated in theappended claim.

I claim:

A process of making a projection welding composite electrical make-andbreak contact comprising (a) placing a silver contact facing element inan indentation in a blank of weldable steel base material having ahigher melting point than the material of the facing element, saidindentation including a bottomwall having a central concave-shapeddepression 4 and a peripheral concave-shaped depression formed therein;

(b) heating said base material and said facing element to liquefy saidfacing element and cause the material thereof to flow along the walls ofthe indentation and fuse to the abutting base material, the surface ofthe fused facing element remote from the bottom wall of said indentationbeing convex in shape and having a peripheral edge portion defining aconcave meniscus Within said-indentation;

(c) moving a concave-shaped punch against the resulting composite fusedelement with a force sufficient to shear the same from the remainder ofthe blank of weldable base material and with continuous progression ofsaid punch compressing the sheared.

composite fused element between said punch and a coining die disposedadjacent the base material portion of said sheared composite fusedelement and having a concave central depression, to form the desiredcontact having a facing element of substantially uniform thickness.

References Cited by the Examiner UNITED STATES PATENTS 2,137,617 11/1938Imes et a1. 29l55.55 2,545,352 3/1951 Gilbbs 29-15555 2,953,247 9/1960Walter et a1 29155.55 X

References Cited by the Applicant UNITED STATES PATENTS 1,130,077 3/1915Eldred. 2,049,771 8/ 1936 Gwyn.

' 2,715,169 8/1955 High.

2,744,180 5/ 1956 Sullivan. 2,832,127 4/1958 Felts et al. 2,925,6472/1960 Jones et a1.

JOHN F. CAMPBELL, Primary Examiner.

WHITMORE A. WILTZ, Examiner.

R. W. CHURCH, Assistant Examiner.

